Stress Profiler Validity Information

Below is a letter from Dr. Kenneth Linfield from Spalding University which states his research for the validation of The Stress Profiler...

Mr. James Porter
Audio Vision
3 Morningside Place
Norwalk, CT 06854

Dear Mr. Porter,

I am pleased to report the following preliminary psychometric information on the Stress Profiler. The temporal stability (test-retest
reliability) and the internal consistency (Cronbach's alpha) of the overall score on stress are excellent (r12=0.92 and a=0.95).

Further,
the temporal stability of the ten subscales
ranges from very good to excellent (0.78 to
0.93), and the internal consistency of those
subscales ranges from good to very good (0.69
to 0.84).

Please
find enclosed a more detailed description of
these psychometric properties, including a
complete table of the estimates for each
subscale and the total score, as well as my
abbreviated curriculum vitae.

As
we have discussed, it is clear that the Stress
Profiler is a very useful measure of stress
because it is so user-friendly. In my use of it with students and in occupational consulting
projects, those who have taken it have
consistently reported finding it to be a very
helpful measure partly because of the clear
descriptions of stress levels and suggested
coping strategies. Further, the data I have summarized
suggests that it is a psychometrically sound
measure of stress as well. As such, I plan to continue to collect
data on its reliability and validity, and to
report that information to you when it is
available.

Best
wishes for continued success with your fine
measure.

Sincerely,

Kenneth J. Linfield, Ph.D.
Assistant Professor
School of Professional Psychology

Description of Psychometric Properties of the Stress Profiler

Kenneth J. Linfield, Ph.D.

The
reliability estimates for the Stress Profiler
listed in Table 1 are based on the responses by
students enrolled at Spalding University during
the 2003 calendar year. The temporal stability estimates
(test-retest reliability correlations) are based
on the responses by 20 graduate students
enrolled in Fall 2003 and 20 undergraduate
students enrolled in Spring 2003 who completed
two administrations of the Stress Profiler two
weeks apart.

The
internal consistency estimates (Cronbach alpha)
are based on the responses from the first
administration of the above groups as well as a
single administration to 28 undergraduate
students enrolled in a class during Fall 2003. The test-retest group was predominantly
female (n=29, 72.5%), and Caucasian (n=30, 75%)
with a range of ages from 17 to 38. >The internal consistency group was also
predominantly female (n=47, 69.1%) and Caucasian
(n=53, 77.9%), with an age range also from 17 to
38.

Table 1

Scale

Test-Retest
ReliabilityPearson
Correlation Coefficients, n=40

Internal
ConsistencyCronbach alpha, n=68

1

0.84

0.73

2

0.88

0.81

3

0.82

0.69

4

0.81

0.81

5

0.88

0.83

6

0.78

0.84

7

0.78

0.79

8

0.85

0.74

9

0.87

0.69

10

0.93

0.76

Total
score

0.92

0.95

Temporal
stability is generally seen as the primary
indication of the reliability or consistency of
any measure.It is based on the assumption that
measures of important constructs (like stress or
intelligence or personality) should yield
similar results when the construct is assessed
at two times, as long as the times are close
enough that the underlying construct would not
be expected to change substantially.

Although
there is no single length of time that is ideal
for test-retest reliability for the construct of
stress measured by the Stress Profiler, the span
of two weeks was chosen both to be short enough
that stress level should not have changed
substantially and long enough to reduce the
degree to which respondents relied on their
memory of their previous response.

The
estimate of 0.92 for the total Stress Profiler
score is an indication of excellent temporal
stability, suggesting that the test is a highly
consistent measure.The generally slightly lower estimates
for the subscales, ranging from 0.78 to 0.93,
show very good to excellent temporal stability,
suggesting that even breaking the general
construct of stress into the ten components of
the Stress Profiler, something that normally
reduces reliability, still results in consistent
measures.

Description
of Psychometric Properties of the Stress
Profiler

Internal
consistency is generally seen as another
important indication of the consistency of
measures.It
is based on the assumption that the various
items used to measure particular aspects of any
construct should show similar patterns of
results.There are a variety of specific ways to calculate estimates
of internal consistency, although they all
indicate the degree to which respondents show
similar response to the various items.

That
is: the degree to which people who score high on
any given item also score relatively high on
other items in the same scale, while those who
score low on the first item also score
relatively low on the other items.

One
simple way to calculate an estimate of internal
consistency is to split a scale into half,
calculate individuals' scores on each half,
and then calculate the correlation between the
scores on each half.This is called "split-half
reliability".

A
more common measure that follows this principle
recognizes that any given method of dividing the
items into two halves of the scale may result in
a stronger or weaker correlation than an
alternate method with the same items.For example, in a scale of ten items, one
could use the first five and the second five, or
the five odd and the five even items.

One
of those methods would likely give a slightly
higher estimate with the other one giving a
slightly lower one simply because of the
particular responses to the various items.To avoid the error of a given method, all
possible methods of splitting the scale into two
halves are used, and the average of all
correlations is calculated.This is called the Cronbach alpha.

The
Cronbach alpha for the entire scale of the
Stress Profiler is 0.95, indicating that the
entire scale is highly internally consistent.People who score high on half of the 100
items tendvery strongly to score high on the other
half, and those who score low on one half
likewise tendvery strongly to score low on the other.The alpha estimates for the ten subscales
would be expected to be lower because a greater
number of items in a scale leads to higher
Cronbach alphas even when the tendency of people
to respond in similar ways across items remains
the same.

In
general, however, the internal consistency
estimates of the subscales from 0.69 to 0.84
show good to very good internal consistency.These estimates, especially in
combination with the very good estimates of
test-retest reliability, show that the Stress
Profiler is a very consistent measure.

Biography

Kenneth
J. Linfield earned his Ph.D. in clinical
psychology at the University of Illinois at
Urbana-Champaign in 1999, and now serves as an
assistant professor in the School of
Professional Psychology at Spalding University
in Louisville, Kentucky. With his minor in quantitative
psychology, he teaches graduate courses in
psychometrics of psychological assessment and
one of the sections of the research sequence in
addition to a range of undergraduate courses.He is the principle investigator on
multiple projects (Assessment of Spiritual Well
Being in a Community Mental Health Center
population, Temple Care II an action
research project on health psychology
interventions, and Development of Screening and
Career Assessment Measures for Clergy and
Missionaries).In addition, he has served as the
statistical consultant on several others (The
Early Intervention Project, CARE I and CARE II,
Development of the Operating Style Assessment)
as well as assessing the psychometric properties
of the Stress Profiler.